Question

Magnesium in chlorophyll molecule is located in
A. Centre of porphyrin head
B. Corner of porphyrin head
C. Phytol tail
D. None of the above

Answer 1

Hint:- Magnesium ions are surrounded by the 4 nitrogen atoms of the pyrrole ring and these are therefore present in the centre. It defines the structure of a chlorophyll molecule.

Complete answer:
First of all, you should know what chlorophyll is. Chlorophyll is a green pigment which is present in all the green plants and in cyanobacteria, it is considered as one of the photosynthetic pigments which is responsible for the absorption of light to provide energy for photosynthesis. Generally chlorophyll and carotenoids are photosynthetic pigments out of which chlorophyll is considered as primary pigment.
It was discovered that the chlorophyll has a tadpole-like configuration i.e., it has a head which is known as porphyrin and it also has a tail which is made up of a long chain of alcohol known as phytol.
It was also observed that the porphyrin head is made of four pyrrole rings and each of the pyrrole rings has 4 carbon atoms and 1 nitrogen atom which means that there are 4 nitrogen atoms in porphyrin head since it consists of 4 pyrrole rings. These 4 nitrogen atoms surround and bind the magnesium ions which means that magnesium is located in the centre of the porphyrin head in a chlorophyll molecule and it defines the structure of a chlorophyll molecule.
If we look at options now, Option A is the correct one since Option A is Centre of porphyrin head and these magnesium ions are surrounded by 4 nitrogen atoms present in the pyrrole of porphyrin head which means that the magnesium ion is present in the centre and also in the porphyrin head which make option A the correct one.
Option B is Corner of porphyrin head. It is incorrect since magnesium is present in the porphyrin head but not in the corner of it. It is present in the centre of the porphyrin head.
Option C is Phytol tail. It is an incorrect option since the magnesium is not present in the tail but it is present in the head which is the pyrrole head. Therefore, this option gets eliminated.
Last option D is none of the above which is also incorrect since from the options, Option A given is the correct one.
Thus, the correct answer is option A which is Centre of porphyrin head.

Note:- In the porphyrin head of tadpole like chlorophyll molecule, there is presence of 4 pyrrole rings and each of these rings, there is presence of one nitrogen atom which makes a total of four nitrogen atoms in the porphyrin head. These atoms surround the magnesium ion which makes the position of magnesium in the centre of the porphyrin head.